1. Field of the Invention
This invention relates to agents for preventing the formation of gray hairs by application to the skin, particularly, agents for preventing the formation of gray hairs which contain an unsaturated fatty acid as an active ingredient.
2. Description of the Prior Art
Gray hair is generally observed in elderly people. It impresses people with the depth of personal character owing to an advanced age. On the other hand, however, it gives an aged impression, and particularly the gray hairs of younger people are unfavorable in general. To hide gray hairs, many studies have been made on hair dyes and many products have been on the market. Hair dyes, however, give only temporary relief, and dyeing must be repeated with the growth of gray hairs. In addition, hair dyes of the oxidative type widely used at present tend to injure the skin by the action of oxidants involved.
Under these circumstances, many studies have been made on agents which substantially prevent the formation of gray hairs.
These include agents containing plant extracts as active ingredients, such as agents prepared from black sesame, leaves of Japanese black pines, and sea tangles (Japanese Patent Kokai No. 87515/1981); agents comprising extract of mustard leaves (Japanese Patent Kokai No. 79617/1981); agents comprising extract of Japanese green gentian (Japanese Patent Kokai No. 70605/1984); agents comprising extract of Acathopanax sieboldianus (Japanese Patent Kokai No. 178805/1985); and agents comprising extract of Angelica keiskei Koidzumi (Japanese Patent Kokai No. 77307/1987). Also disclosed are agents comprising pituitary hormone (Japanese Patent Kokai No. 63510/1987); agents comprising 3-(3,4-dihydroxyphenyl)-L-alanine (Japanese Patent Kokai No. 63509/1987); agents comprising C-AMP (cyclic adenosine 3',5'-monophosphate) (Japanese Patent Kokai No. 45527/1987); agents comprising vitamin D3 (Japanese Patent Kokai No. 174705/1985), and agents comprising minoxidyl (Japanese Patent Kokai Nos. 165310/1986 and 227518/1986).
The active ingredients used in these conventional agents are mainly plant and animal extracts, or animal components that participate in biological activities. Hence, there are some limitations upon the manufacture of these compounds, and their effects are inconsistent and not satisfactory.